To assess the influence of age and education on cognitive performance in our population, 530 adults were interviewed using the MMSE (Mini-Mental Status Examination). Education level, classified as illiterate, elementary and middle (< 8 years) and high (> 8 years), was a significant predictor of performance (p < 0.0001). Nevertheless, the total scores were not significantly different among the age-groups, young (< or = 50 years), middle age 51 to 64 years) and elderly (> or = 65 years). The reference cut-off values were taken from the fifth percent lowest score for each group: illiterate, 13; elementary and middle, 18; and high, 26. When compared to 94 patients with cognitive impairment, our cut-off values achieved high sensitivity (82.4% for illiterates; 75.6% for elementary and middle; 80% for high) and specificity (97.5% for illiterate; 96.6% for elementary and middle; 95.6% for high educational level). Education-specific reference values for the MMSE are necessary in interpreting individual test results in populations of low educational level, in order to reduce the false positive results.